1. Field
The present invention relates to an image scanning apparatus, an image forming apparatus and an image scanning method for simultaneously scanning both sides of an original document.
2. Description of the Related Art
Some image scanning apparatus such as a scanner and some image forming apparatuses such as a copy machine can simultaneously scan both sides of an original document. These image scanning apparatuses and image forming apparatuses have a face-side scanning unit that scans an image (hereinafter referred to as a face-side image) printed on one side (face side) of an original, and a back-side scanning unit that scans an image (hereinafter referred to as a back-side image) printed on the back side of the original.
In the image scanning apparatuses and image forming apparatuses of this type, for example, the face-side scanning unit and the back-side scanning unit are arranged facing each other. As an original is carried between the face-side scanning unit and the back-side scanning unit, both sides of the original can be scanned simultaneously.
Meanwhile, originals with printing done on both sides (hereinafter referred to as double-side originals) include two types of originals, depending on the top-bottom (up-down) relation of the face-side image and the back-side image.
The first type of double-side original is a so-called left-right binding type (hereinafter, referred to as a booklet type) in which the face-side image and the back-side image have the same up-down direction when the original is rotated by 180 degrees to an axis parallel to the up-down direction of the face-side image.
The second type of original is a so-called up-down binding type (hereinafter referred to as a tablet type) in which the face-side image and the back-side image have the same up-down direction when the original is rotated by 180 degrees to an axis perpendicular to the up-down direction of the face-side image (an axis parallel to the left-right direction). On the back side of the tablet type original, the image is rotated by 180 degrees, compared with the back side of the booklet type original.
Generally, the main scanning direction and the sub scanning direction of the face-side scanning unit and the back-side scanning unit are defined in advance in one direction each. Therefore, for example, in the case where each scanning direction of the face-side scanning unit and the back-side scanning unit is decided in such a way that images on the face side and the back side of a booklet type original can be acquired normally, for a tablet type original, the face-side image can be acquired normally but the back-side image is rotated by 180 degrees when it is acquired.
Conventionally, as a technique to correct an image that is rotated by 180 degrees or inverted in the left-right direction to an image with a normal up-down direction and left-right direction when simultaneously scanning both sides of an original (hereinafter referred to as normalization of image direction), after an image on each of the face side and the back side is scanned, the direction of the image can be normalized by proper rotation of the image or the like.
With the conventional technique, the scanned face-side image and back-side image can be stored in a storage medium such as a hard disk, with their up-down and left-right directions aligned. Therefore, with the conventional technique, various processing can be easily carried out on the basis of the scanned images, such as printing the image onto a recording paper, or creating and editing an image file.
In the conventional technique, however, in order to normalize the image direction, it is necessary to read out an image from a page memory after it is scanned and stored into the page memory, and then to normalize the image direction and store the image into a storage medium such as a hard disk. Therefore, it takes time to acquire a normal image. Thus, in the conventional technique, it takes time to simultaneously scan both sides of an original and execute various processing based on the scanned images, for example, when taking double-side copy of a double-side original.